I was hearing the other two crabs, who are alive and eating like pigs. Thank you all for your advice and I did my best to follow it even though I'm terrible at updating back here, but I'm afraid Jupiter is dead. I don't think there was much anything I could have done. It could be that the other crabs pestered him too much when I wasn't looking or it was just over-stress. I'm not sure if he tried to molt, probably just destressing because the other two were buried for just as long and they haven't molted. Jupiter was always the one to get pushed around and he was much gentler then those other two little monsters, so I'm not surprised. I am going to look over my tank and consider either a deep clean or a new (bigger) tank altogether just in case there was something wrong (and there are improvements I need to make, it's not perfect), but I think this was just a case of bad luck with a new crab for a newbie...I usually cry when my pets die, but I haven't yet. I'm sure I'm going to start bawling in about an hour.